R posterior of interatrial septum. Innervated by autonomic parasympathetic ganglia. Causes beginning of systole.

Conducting fibers from AV node converge to form ____. Triangular shaped. W/in posterior border interventricular septum. Lower ends form R & lower bundle branches.

Terminal branches of the R & L bundle branches. Extend from the ventricular apexes to the fibrous rings and penetrate the heart wall to the outer myocardium.

Activated by the R and L branches of the AV bundle.

Extensive network of Purkinje fibers promotes rapid spread of the impulse to the ventricular apexes. Activation traverses the wall from the inside out.

These portions are the last to be activated.

During diastole in the opposite direction.

Which of the following are correctly matched?

Movement of ions into and out of the cell creates an electrical (voltage) difference across the cell membrane called the ________.

During depolarization the __(1)__ of the cell becomes less __(2)__ charged.

In cardiac cells the difference between resting membrane potential and the decreased negative charge caused by depolarization is the ______.

Myocardial fibers have which of the follwing?

Phases of Depolarization of Myocardial Cells: Rapid depolarization (E)

Phases of Depolarization of Myocardial Cells: An initial rapid repolarization (D)

Phases of Depolarization of Myocardial Cells: A plateau (C)

Phases of Depolarization of Myocardial Cells: A slow repolarization process (B)

Phases of Depolarization of Myocardial Cells: Return to the resting membrane potential (A)

Myocyte Action Potentials: Ions from adjacent cells leak through gap junctions which makes myocyte membrane potential to reach -70 mV (threshold).

Myocyte Action Potentials: Fast sodium channels open -> rapid influx sodium into cell.

Myocyte Action Potential: When the membrane reaches __(1)__ the __(2)__ open.

Myocyte Action Potentials: Fast sodium channels close. Slow calcium channels remain open.

Myocyte Action Potentials: Voltage-gated K+ channels open to allow K+ out of the cell.

Myocyte Action Potentials: Movement Ca2+ and K+ are balanced, which causes the membrane potential to remain stable for about 200 ms.

Once __(1)__ close, __(2)__ efflux causes repolarization of the myocyte and returns it to resting potential.

Pacemaker Action Potential: Funny channels open when potential goes below -40 mV to allow for a slow influx of Na+. Causing depolarization to take cell to threshold.

Pacemaker Action Potential: Funny channels close. Calcium channels open. Further depolarization.

Pacemaker Action Potential: K+ leaves cell to cause voltage to return to -60 mV. Several ion pumps restore original ion gradients. Cycle starts again.

Enables SA & AV nodes to generate cardiac action potentials w/o external stimulus

Regular generation action potential by heart’s conduction system

Atrial depolarization & conduction through AV node (4)

Time from onset atrial activation to onset ventricular activation. Time necessary for electrical activity to travel from sinus node through atrium, AV node, His-Purkinje to activate myocardial cells. (1)

Sum all ventricular muscle cell depolarization. Configuration and amplitude vary considerable among individuals. (2)

Ventricular repolarization (7)

Entire ventricular myocardium is depolarized (6)

Electrical systole of ventricles (3)

__(1)__ stimulation __(2)__ electrical conductivity and strength myocardial contraction.

____ stimulation of the heart depends on the presence of G-protein-coupled adrenergic receptors (β1, β2, β3, 𝛼1, 𝛼2).

Which of the following stimulate sympathetic?

Which predominates in the heart?

Which is found in the heart and on vascular smooth muscle?

Pacemaker cells: _____ facilitates conductance of sodium and calcium in pacemaker cells, causing the slope of the porepotential to increase, leading to increased number of depolarizations over time.

Pcaemaker cells: ______ facilitates the conductance of K+, which causes the slope of the prepotential to decrease, leading to decreased number of depolarizations over time.

__(1)__ activity __(2)__ action potential & reduces strength contraction.

Adrenaline

Acetylcholine